Cork composition and method of making



Patented Jan. 31, 1950 2,495,755 com; comeoslrmn AND METHOD or MAKING Herbert Paschke, Manheim Township, Lancaster County, Pa., assignor to Armstrong Cork Company, Lancaster, vania Pa., a corporation of Pennsyl- No Drawing. Application September 12, 1946, I

Serial No. 696,623

13 Claims.

The present invention relates to a cork composition and the method of making it. The term cork composition is commonly used in the industry as descriptive of compositions made by pressing granulated cork with a suitable binder into various shapes, usually in the form of mats, which are usually out to the desired form. The principal use for cork compositions is the making of gaskets for mechanical purposes and the liners for the Crown type bottle closures.

According to the usual practice of making cork composition, granulated cork, which mayvary from to 40 meshes to the inch of United States standard screen, is used. 100 parts of granulated cork by weight are put into a suitable mixer. Then there is added a water solution containing about parts of glycerine and about 6 /2 parts 01' glue by dry weight. A sufficient amount of water is used to effect proper solution of the glue and glycerine. This solution is poured hot into the mixer and thoroughly mixed with the cork. At the conclusion of this mixing an aldehydeyielding substance, usually paraformaldehyde, is added to an amount of about 0.6% of the weight of the cork. The mixing is continued and the mixed mass is put into molds where it is compressed and heated to cure the binder. The usual size of mold is 24 x 36 x 3 inches. The curing period is usually about 6 /2 hours at a temperature of the oven in which the molds are placed of about 240 to 250 F. This heating cycle generates formaldehyde gas from the paraformaldehyde and causes it to tan the glue. Such tanning is important to convert the glue into a substantially water-insoluble condition. A piece of the composition cork will withstand boiling in water for three hours without disintegration. After the curing operation the molds are cooled, the mats removed and sliced into sheets .of'th desired thickness for gaskets, bottle cap liners, etc. While this process has produced cork composition which has been heretofore acceptable, the curing temperature causes the cork to be somewhat darkened so that the cork composition does not have the attractive light-colored ap pearance of natural cork. The darkening of the cork composition indicates incipient carbonization and degradation of the quality of the cork.

However, a curing cycle of the time-temperature given above has been required to cause the formaldehyde to tan the glue sufficiently to achieve the requisite water insolubility of the glue.

I have found that a cork composition improved both in color and in physical characteristics may be produced by the substitution of resorcinol or other dihydroxy-benzenes for a part of the glue.

I have found that such substitution allows the curing to be carried out at a substantially lower temperature than heretofore used, resulting in a cork composition having the light color of natu- A preferred procedure in carrying out my invention is to place parts of granulated cork of from 5 to 40 meshes to the inch of United States standard screen in a mixer as heretofore and to add to such granulated cork a solution containing 20 parts glycerine, 4 parts of glue by dry weight and 1 part of resorcinol in a sufficient quantity of water to make the proper solution. The resorcinol appears to reduce the viscosity of the glue and aids in its distribution over the cork granules. This solution is preferably added hot. After the solution has been thoroughly mixed with the granulated cork, A; part by weight of powdered paraformaldehyde is sprinkled on the mass of cork and thoroughly mixed. After mixing, the mass is put into the usual mat molds, compressed, and heated. The heating cycle, however, has a substantially reduced temperature over that heretofore used, being preferably 6 /2 hours at about 200 F. After the heating is completed, the molds are cooled, opened, and the mats are out up in the usual Way to form gaskets, bottle cap seals, etc. The final product consists of compressed cork granules which are softened by the glycerine and are bonded together by the heat reaction product of the glue, resorcinol and paraformaldehyde, the bond consisting of the tanned glue and the resorcinolaldehyde resin.

Instead of adding the paraformaldehyde after the solution of glycerine, glue and resorcinol is mixed with the granulated cork. the ingredients may all be added at the same time. It is preferred, however, to add the paraformaldehyde after the glycerine, glue and resorcinol have been mixed with the cork because of the very rapid reaction which takes place between the paraformaldehyde and the resorcinol. In either of these methods. the resorcinol-formaldehyde resin is formed in situin the mix. The resorcinol has the great advantage of a very quick reaction with thealdehyde so that only a relatively low temperature is required to form the resin.

-While I have found that a curing cycle of 6 /2 hours at 200 F. is satisfactory in making mats of the usual dimensions, which are approximately 3 inches thick, the heatingmay be varied so long the reaction between the paraformaldehyde, resorcinol and glue takes place. While the heat" ing may be somewhat more than 200 F. over a short period, it is preferred to keep the heat at a temperature of about 200 F. and not substantially'in' excess of 210 F. and vary the time of heating,depending upon the thickness of the cork mass being treated and the character of the-heat ing. For example, thin sheets may be cured in a considerably shorter time than 6 hours. Other heating may be employed such'as 'high frequency dielectric heating, in which case the curing cyclemay be shortened.

ral cork and having improved physical properties. The reduction-in thecuring temperatureof about 40 to 50 F. is substantial and is enough so that the darkening of the cork composition as heretofore encountered is obviated and the cork composition appears to have the same light color as the natural cork. This is a very important feature from the sales standpoint, as buyers will buy cork composition largely upon its appearance.

The paraformaldehyde apparently has a double function of combining with the resorcinol to form a resorcinol-aldehyde resin and to also chemically combine with the glue to tan it. The tanning of the glue at the lower temperature, which Ihave found to be possible by the partial substitution of resorcinol for the glue, is carried as fully to completion as with the higher curing temperature of the prior practice, as shown by extraction tests in which the cork composition is boiled in hot water, such as in the usual test of boilin for 3 hours. Not only does the glue appear to be tanned to a fully insoluble state but the bond is improved over a simple glue bond, particularly the resistance of the bond to acids and to weathering. A piece of the cork composition may be boiled in a 5% hydrochloric acid or 5% citric acid solution for 1 hour without disintegration, whereas the .same acid treatment would disintegrate the usual glue-bonded cork compositions ina matter of a fraction of anhour.

I am not certain of the exact interaction be tween the paraformaldehyde, resorcinol and glue. It may be that the resorcinol-aldehyde resin has some catalytic action which speeds up the tanning of the glue by the formaldehyde, or it may be that the resorcinol-formaldehyde resin which forms quickly has some protective action upon the glue. Whatever may be the theory, the fact is that not only is the process carried out at a lower temperature but the composition is more resistant to attack, such as by dilute acids or by weathering.

The resistance against acids and weathering may be further increased by substituting more resorcinol for a part of the glue. For example, a formula of parts glycerine, .3 parts glue (dry Weight) 2 parts resorcinol, and 1 part para formaldehyde to 100 parts of cork when mixed and cured for 6 /2 hours at 200 F. produces a cork composition which will withstand boiling in concentrated hydrochloric acid for hour without disintegration of the bond. The bond has a correspondingly increased resistance to weathering, which is an important characteristic where gaskets are used for closures which are used out of doors. The substitution of the resorcinol for a part of the glue also imparts'resistance to the action of molds.

The 20 parts of glycerine above stated is mentioned as an illustrative example of a cork composition suitable .for gaskets and bottle closures. The amount of glycerin can be varied as is usual in the art, depending upon the particular use to which the cork compositions are employed, .such ranges being from about 5 to 30, usually from 10 to 20. While glycerine is the substance usually employed for softening the cork granules and as a humectant, other compatible cork-softening agents may be employed, such as the polyhydric alcohols, particularly the glycols which are watersoluble and capable of going into water solution with the glue and resorcinol. While glycerine or other cork-softening agent is commonly employed in cork compositions, the softening agent may be omitted for special compositions, such as for cigarette tips, pulley facings, etc.

Animal glue is the usual and preferred material for making cork compositions and I prefer to employ it. However, other proteins of either animal or vegetable origin, such as casein, soya bean protein and zein, may be used to replace some or all of the glue of my composition. In general, any protein which is tannable by an aldehyde may be employed. The amount of glue may be varied, depending upon the desired strength of the bond, as from 2 to 15 parts to parts of cork by weight, preferably from 3 to 6 parts of glue.

While resorcinol is preferably used, other dihydroxybenzenes may be used, such as catechol and hydroquinone. The amount of resorcinol added in general varies inversely with the amount of glue. In the first specific example one part of resorcinol was used, together with 4 parts of glue to 100 parts of cork by weight, while in the second example 2 parts of resorcinol were used, together with 3 parts of glue to 100 parts of cork. It is possible, however, to use resorcinol within wider limits as from 1 to 15 parts of resor cinol with 100 parts of cork by weight, preferably from 1 to 3 parts of resorcinol.

The paraformaldehyde should be used in an amount sufficient to combine with the resorcinol to form a resorcinol-aldehyde resin, leaving a sufficient excess to tan the glue. I have found that this condition will be satisfied in most of my mixes by the use of 1 part of paraformalde hyde to 2 parts of resorcinol. However, this may be varied, particularly if a large quantity of glue is employed, which would require a considerable excess of paraformaldehyde to tan it above that required for combination with the resorcinol. The amount of paraformaldehyde may therefore be varied within fairly wide limits as from A; to 11/ parts of paraformaldehyde to 100 parts by weight of cork, preferably from A to /2 part of paraformaldehyde.

While paraformaldehyde is preferred because of the ease of handling, other aldehyde-yielding substances may be employed since the aldehyde constituent combines with the resorcinol to form a resinous product and also combines with the protein to tan it. When other aldehyde-yielding substances are used the proportion should be correlated to the resorcinol according to the avail able aldehyde group. Other suitable aldehydeyielding substances are formaldehyde, acetaldehyde, benzaldehyde, furfural, hexamethylenetetramine, aldehyde-ammonia and the like, or mixtures of these compositions. While my binder consisting of the heat reaction product of the protein, dihydroxy-benzene and aldehyde is preferably employed alone, it may be used in combination with other binders, in which case it should be the principal part of the binder.

While I have specifically described the preferred embodiment of my invention, it is understood that the invention may be otherwise embodied and practiced within the scope of the following claims.

I claim:

1. A cork composition comprising by weight 100 parts of compressed cork granules, 10 to 20 parts of glycerine and the heat reaction product of 3 to 6 parts of glue, 1 to 3 parts of resorcinol .and a suificient amount of paraformaldehyde, between A and 7 parts, to combine with the resorcinol to form a resorcinol-aldehyde resin and to tan the glue.

2. ,A cork composition comprising by weight 100 parts of compressed cork granules, 5 to .30 parts of glycerine and the heat reaction product of 2 to 15 parts of glue, 1 to 15 parts of resorcinol and a sufficient amount of paraformaldehyde, between and 7%; parts, to combine with the resorcinol and to tan the glue.

3. A cork composition comprising by weight 100 parts of compressed cork granules, to 20 parts of a cork softening agent and the heat reaction product of 3 to 6 parts of glue, 1 to 3 parts of resorcinol and a sufiicient amount of an aldehyde, between A, and 7 parts, to combine with the resorcinol and to tan the glue.

4. A cork composition comprising by weight 100 parts of compressed cork granules, 5 to 30 parts of a cork softening agent and the heat reaction product of 2 to parts of a water-soluble protein. 1 to 15 parts of an unsubstituted dihydroxybenzene and a sufficient amount of an aldehyde, between A; and 7% parts, to combine with the unsubstituted dihydroxy-benzene and to tan the water-soluble protein.

5. A cork composition comprising by weight 100 parts of compressed cork granules and the heat reaction product of 3 to 6 parts of glue, 1 to 3 parts of resorcinol and a sufficient amount of paraformaldehyde, between A; and 7 /2 parts, to combine with the resorcinol and to tan the glue.

6. A cork composition comprising by weight 100 parts of compressed cork granules and the heat reaction product of 2 to 15 parts of a Watersoluble protein, 1 to 15 parts of resorcinol and a sufficient amount of an aldehyde, between A and 7% parts, to combine with the resorcinol and to tan the water-soluble protein.

'7. A cork composition comprising by weight 100 parts of compressed cork granules and the heat reaction product of 2 to 15 parts of a watersoluble protein, 1 to 15 parts of an unsubstituted dihydroxy-benzene and a sufficient amount of an aldehyde, between A; and 7% parts, to combine with the unsubstituted dihydroxy-benzene and to tan the water-soluble protein.

8. The method of making a cork composition which comprises: mixing by weight 100 parts of cork granules with a water solution containing 10 to parts of glycerine, 3 to 6 parts of untanned glue, and 1 to .3 parts of rescorcinol; after the water solution has been distributed over the cork granules, adding to the coated cork granules and mixing in to 7 /2 parts of paraformaldehyde; compressing the mixture; and heat curing it at a temperature not in eXcess of about 210 F. to combine the aldehyde with the unreacted resorcinol to form a resorcinol-aldehyde resin and to tan the untanned glue and thus form in situ a binder which will permit the cork composition to be boiled in a 5% hydrochloric acid solution for one hour without disintegration.

9. The method of making a cork composition which comprises: mixing by weight 100 parts of cork granules with a water solution containing 5 to 30 parts of glycerine, 2 to 15 parts of untanned glue, and 1 to 15 parts of resorcinol; after the water solution has been distributed over the cork granules, adding to the coated cork granules and mixing in A; to 7 /2 parts of paraformaldehyde; compressing the mixture; and heat curing it at a temperature not in excess of about 210 F. to combine the aldehyde with the unreacted resorcinol to form a resorcinol-aldehyde resin and to tan the untanned glue and thus form in situ a binder which will permit the cork composition to be boiled in a 5% hydrochloric acid solution for one hour without disintegration.

10. The method of making a cork composition which comprises: mixing by Weight parts of cork granules with a water solution containing 5 to 30 parts of a cork softening agent, 2 to 15 parts of untanned glue, and 1 to 15 parts of resorcinol; after the water solution has been distributed over the cork granules, adding to the coated cork granules and mixing in A; to 7 parts of paraformaldehyde; compressing the mixture; and heat curing it at a temperature not in excess of about 210 F. to combine the aldehyde With the resorcinol to form a resorcinol-aldchyde resin and to tan the untanned glue and thus form in situ a binder which Will permit the cork composition to be boiled in a 5% hydrochloric acid solution for one hour without distintegration.

11. The method of making a cork composition which comprises: mixing by weight 100 parts of cork granules with a water solution containing 5 to 30 parts of a cork softening agent, 2 to 15 parts of an untanned water-soluble protein, and 1 to 15 parts of an unreacted, unsubstituted dihydroxy-benzene and with A; to 7 /2 parts of an aldehyde; compressing the mixture; and heat curing it to combine the aldehyde with the unreacted, unsubstituted dihydroxy-benzene to form a dihydroxy-benzene resin and to tan the untanned water-soluble protein and thus form in situ a binder which will permit the cork composition to be boiled in a 5% hydrochloric acid solution for one hour Without disintegration.

12. The method of making a cork composition which comprises: mixing by weight 100 parts of cork granules with a water solution containing 10 to 20 parts of a cork softening agent, 3 to 6 parts of glue, and 1 to 3 parts of resorcinol and with A to 7 parts of paraformaldehyde; coimpressing the mixture; and heating it to combine a portion of the aldehyde with the resorcinol to form a resorcinol-aldehyde resin and to tan the glue and. thus form in situ a binder which will permit the cork composition to be boiled in a 5% hydrochloric acid solution for one hour without disintegration.

13. The method of making a cork composition which comprises: mixing by Weight 100 parts of cork granules with a water solution containing 2 to 15 parts of an untanned water-soluble protein and 1 to 15 parts of an unreacted, unsubstituted dihydroxy-benzene and with A; to 7 /2 parts of an aldehyde; compressing the mixture; and heat curing it to combine the aldehyde with the unreacted, unsubstituted dihydroxy-benzene to form a dihydroxy-benzene resin and to tan the untanned water-soluble protein and thus form in situ a binder which will permit the cork composition to be boiled in a 5% hydrochloric acid solution for one hour without disintegration.

HERBERT PASCI-IKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,013,698 Paschke et a1 Sept. 10, 1935 2,038,113 Irey Apr. 4, 1936 2,053,850 Sturken Sept. 8, 1936 2,104,692 Cooke et a1 Jan. 4, 1938 2,121,791 Frink June 28, 1938 2,375,008 Lawrence May 1, 1945 2,385,374 Rhodes Sept. 25, 1945 2,443,197 Rhodes June 15, 1948 

2. A CORK COMPOSITION COMPRISING BY WEIGHT 100 PARTS OF COMPRESSED CORK GRANULES, 5 TO 30 PARTS OF GLYCERINE AND THE HEAT REACTIONPRODUCT OF 2 TO 15 PARTS OF GLUE, 1 TO 15 PARTS OF RESORCINOL AND A SUFFICIENT AMOUNT OF PARAFORMALDEHYDE, BETWEEN 1/4 AND 7 1/2 PARTS, TO COMBINE WITH THE RESORCINOL AND TO TAN THE GLUE. 